1. Field of the Invention
The present invention relates to an elastic pressing unit and a molded case circuit breaker having the same, and particularly, to an elastic pressing unit capable of preventing deformation of a component and thus avoiding a loose (poor) contact between contacts due to the deformation, and a molded case circuit breaker having the same.
2. Background of the Invention
In general, a molded case circuit breaker is installed at a switch board or the like so as to serve as a switching mechanism for supplying or cutting off power toward a load side in a no load condition. During the use of load, if a high current exceeding a load current flows due to an abnormal occurrence in a load current path, the molded case circuit breaker serves to supply power from a power source side to a load side or block such power, for the purpose of protecting wires of the load current path or load side components.
FIG. 1 is a disassembled perspective view of a molded case circuit breaker according to the related art, FIG. 2 is a perspective view showing an inside of unipolar blocking units of FIG. 1, and FIG. 3 is a perspective view showing an operation of a rotation pin of FIG. 1. As shown in FIGS. 1 to 3, a molded case circuit breaker includes a plurality of unipolar blocking units 110 configured to control each phase current and having a movement route for allowing an arc pressure to be moved therealong, a mechanical unit 140 configured to operate the unipolar blocking units 110 according to a user's manipulation or by means of a trip mechanism (not shown), and a rotation pin 150 simultaneously coupled to each of movable contacts 131 of the unipolar blocking units 110 so that the movable contacts 131 can be moved at the same time and configured to transfer a driving force of the mechanical unit 140 to each unipolar blocking unit 110.
Each unipolar blocking unit 110 may be provided with a frame 111, a fixed is contact 121 fixed to the frame 111, and a movable contact 131 coupled to the frame 111 to be rotatable from the fixed contact 121. Here, the fixed contact 121 and the movable contact 131 may be configured to have a current limitation performance.
Each movable contact 131 may be rotated centering around a rotation shaft 135, which is rotatably supported at the frame 111. The rotation pin 150 may be coupled to one side of the rotation shaft 135 of the movable contact 131 in parallel to the rotation shaft 135.
The mechanical unit 140 may be configured as a plurality of links and springs (not shown) for generating a driving force applied when the movable contact 131 and the fixed contact 121 are contacted with or separated from each other. A handle 145 for allowing the user's manipulation may be connected to one side, namely, an upper side of the mechanical unit 140. The mechanical unit 140 is connected to the handle 145 and a trip mechanism. Accordingly, the contact or separation between the movable contact 131 and the fixed contact 121 are enabled by the handle 145 manipulated by the user or by means of the trip mechanism.
In the meantime, the unipolar blocking units 110 may be provided in the same number (e.g., three or four unipolar blocking units) as the number of phases. Here, the rotation pin 150 may have a length long enough to be simultaneously coupled to the movable contacts 131 of the unipolar blocking units 110 depending on the number of installed unipolar blocking units 110.
With such configuration, when the handle 145 is moved to a closing position, the rotation pin 150 is rotated by the driving force of the mechanical unit 140, and each movable contact 131 of the unipolar blocking units 110 is simultaneously rotated to the closing position responsive to the rotation of the rotation pin 150. Here, when the movable contact 131 comes in contact with the fixed contact 121, an electric repulsive force is applied between the fixed contact 121 and the movable contact 131. Here, since the driving force of the mechanical unit 140 is greater than the electric repulsive force, the movable contact 131 comes in contact with the fixed contact 121, thereby being able to apply an electric current.
However, in the related art molded case circuit breaker, upon a closing operation, the driving force of the mechanical unit 140 and the electric repulsive force of each unipolar blocking unit 110 are applied to the rotation pin 150 simultaneously in opposite directions. Accordingly, the rotation pin 150 may be deformed. In particular, since the mechanical unit 140 is disposed approximately at a middle portion of the rotation pin 150, the deformation of the rotation pin 150 may occur more severely at a portion (area) of the rotation pin 150 coupled to a unipolar blocking unit 110 disposed far away from the mechanical unit 140 than at a portion thereof coupled to a unipolar blocking unit 110 disposed close to the mechanical unit 140. When the deformation of the rotation pin 150 occurs, the movable contact 131 and the fixed contact 121 of the unipolar blocking unit 110, disposed at the deformed area of the rotation pin 150, may not be contacted with each other by a sufficient contact pressure, which may cause a current to be applied unstably.